在 JavaScript 关联数组中动态创建键

javascript associative-array

2022-08-30 01:16:01

到目前为止，我找到的所有文档都是更新已创建的密钥：

 arr['key'] = val;

我有一个这样的字符串：" name = oscar "

我想以这样的东西结束：

{ name: 'whatever' }

也就是说，拆分字符串并获取第一个元素，然后将其放入字典中。

法典

var text = ' name = oscar '
var dict = new Array();
var keyValuePair = text.split(' = ');
dict[ keyValuePair[0] ] = 'whatever';
alert( dict ); // Prints nothing.

答案 1

不知何故，所有的例子虽然效果很好，但都过于复杂：

他们使用，这是一个简单的关联数组（AKA字典）的过度杀伤（和开销）。new Array()
使用效果越好。它工作正常，但是为什么所有这些额外的输入？new Object()

这个问题被标记为“初学者”，所以让我们让它变得简单。

在JavaScript中使用字典的非常简单的方法或“为什么JavaScript没有特殊的字典对象？”：

// Create an empty associative array (in JavaScript it is called ... Object)
var dict = {};   // Huh? {} is a shortcut for "new Object()"

// Add a key named fred with value 42
dict.fred = 42;  // We can do that because "fred" is a constant
                 // and conforms to id rules

// Add a key named 2bob2 with value "twins!"
dict["2bob2"] = "twins!";  // We use the subscript notation because
                           // the key is arbitrary (not id)

// Add an arbitrary dynamic key with a dynamic value
var key = ..., // Insanely complex calculations for the key
    val = ...; // Insanely complex calculations for the value
dict[key] = val;

// Read value of "fred"
val = dict.fred;

// Read value of 2bob2
val = dict["2bob2"];

// Read value of our cool secret key
val = dict[key];

现在让我们更改值：

// Change the value of fred
dict.fred = "astra";
// The assignment creates and/or replaces key-value pairs

// Change the value of 2bob2
dict["2bob2"] = [1, 2, 3];  // Any legal value can be used

// Change value of our secret key
dict[key] = undefined;
// Contrary to popular beliefs, assigning "undefined" does not remove the key

// Go over all keys and values in our dictionary
for (key in dict) {
  // A for-in loop goes over all properties, including inherited properties
  // Let's use only our own properties
  if (dict.hasOwnProperty(key)) {
    console.log("key = " + key + ", value = " + dict[key]);
  }
}

删除值也很容易：

// Let's delete fred
delete dict.fred;
// fred is removed, but the rest is still intact

// Let's delete 2bob2
delete dict["2bob2"];

// Let's delete our secret key
delete dict[key];

// Now dict is empty

// Let's replace it, recreating all original data
dict = {
  fred:    42,
  "2bob2": "twins!"
  // We can't add the original secret key because it was dynamic, but
  // we can only add static keys
  // ...
  // oh well
  temp1:   val
};
// Let's rename temp1 into our secret key:
if (key != "temp1") {
  dict[key] = dict.temp1; // Copy the value
  delete dict.temp1;      // Kill the old key
} else {
  // Do nothing; we are good ;-)
}

答案 2

使用第一个示例。如果该密钥不存在，则将添加该密钥。

var a = new Array();
a['name'] = 'oscar';
alert(a['name']);

将弹出一个包含“奥斯卡”的消息框。

尝试：

var text = 'name = oscar'
var dict = new Array()
var keyValuePair = text.replace(/ /g,'').split('=');
dict[ keyValuePair[0] ] = keyValuePair[1];
alert( dict[keyValuePair[0]] );